1. Field of the Invention
The invention relates to a differential device, and more particularly, to a differential device that effectively allows suppressing damage to a welded portion between a differential case and a ring gear.
2. Description of the Related Art
A differential device has ordinarily a differential case that houses a gear group, and a ring gear that is disposed fitted to the differential case. The differential case and the ring gear are supported rotatably about a drive shaft. Integral welding of the differential case and the ring gear is a recent trend. Japanese Patent Application Publication No. 2007-192326 (JP-A-2007-192326) discloses a conventional differential device that relies on such a configuration.
Another recent trend is the use of ring gears that have a helical gear. In such a configuration, a thrust load (helical gear-specific thrust load), derived from the helical angle of the helical gear, acts on the ring gear. Thrust load may damage the welded portion of the differential case and the ring gear (for instance, weld detachment).